The late-Paleoproterozoic I- and A-type granites in Lüliang Complex, North China Craton: New evidence on post-collisional extension of Trans-North China Orogen

The late-Paleoproterozoic granitoids from Lüliang Complex can provide pivotal constraints on the amalgamation process between Eastern and Western blocks of North China Craton along the Trans-North China Orogen. LA-ICP-MS zircon dating gives emplacement ages of 1854 ± 20 Ma for the Huijiazhuang granite, 1830 ± 21 Ma for the Xiyupi granite vein and 1760 ± 20 Ma for the Dacaoping porphyritic granite, respectively. The Huijiazhuang granite and Xiyupi granite dyke have variable SiO2 (66.71-74.31 wt%), high K2O (5.09-6.35 wt%), low P2O5 (0.02-0.16 wt%), Al2O3 (13.92-15.31 wt%), right inclined REE patterns with medium negative Eu anomalies, enrichment in LILE, depletion in HFSE, especially Nb, Ta, consisting to high-K I-type granite in a post-collisional setting. The Sr/Y (7.36-59.95), εNd(t) (−5.7 to −4.1) with TDM (2381 Ma to 2570 Ma) from whole rock Sm-Nd isotope and εHf(t) (−9.6 to 2.3) with TCDM (2360 Ma to 3070 Ma) from zircon Lu-Hf isotope suggest that they are produced by partial melting of slightly thickened Neoarchean-Paleoproterozoic basement materials (including both meta-sedimentary and meta-igneous rocks). The Dacaoping porphyritic granites are characterized by high SiO2 (70.83-74.30 wt%), K2O (4.84-5.60 wt%), FeOT/(FeOT + MgO) (0.86-0.92), “seagull-type” REE pattern with strong negative Eu anomaly (δEu=0.16-0.35) and higher 10000∗Ga/Al (2.99-3.36), HFSE (Zr + Nb + Ce + Y = 378-583 ppm), showing an affinity of A2-type granite. They have low Sr/Y (1.17-8.62), εNd(t) (-6.1 to -6.4) with TDM (2690 Ma to 2776 Ma) from whole rock Sm-Nd isotope and εHf(t) (-7.9 to -5.2) with TCDM (2775-2938 Ma) from zircon Lu-Hf isotope, indicating a result from the melting of thinned Neoarchean calc-alkaline intermediate basement. Taking into account the temporal-spatial distributions of late-Paleoproterozoic rocks in the Trans-North China Orogen, it suggests a post-collisional extension occurred during 1.89-1.76 Ga and the crust is thinned visibly since 1.82 Ga.